Effects of drilling parameters and bone density on axial force in a force-feedback-based robotic dental implant osteotomy system: an in vitro cadaveric study

This study investigates the effects of drill diameter, rotation speed, drilling depth, and bone density on axial force during robotic osteotomy using a force-feedback system, providing an experimental basis for real-time monitoring and dynamic compensation in robotic implant surgery. Six fresh frozen cadaveric mandibles were used to prepare 72 drilling sites in bilateral anterior and posterior regions. The Yakebot dental implant robotic system performed drilling with real-time axial force monitoring. Test parameters included three drill diameters (2.0, 3.5, and 5.0 mm), three rotation speeds (600, 1000, and 1500 rpm), and two drilling depths (10 and 13 mm). Bone density (HU value) at each site was measured from preoperative CBCT scans. Linear mixed-effects model analysis demonstrated good fit (marginal R 2 = 0.834; conditional R 2 = 0.882). The intraclass correlation coefficient was 0.287, indicating that 28.7% of variance originated from inter-specimen differences. Main effects analysis revealed that all four parameters significantly influenced axial force ( p < 0.001). Interaction analysis showed a significant negative interaction between speed and diameter ( p < 0.001), indicating that high speed combined with large diameter synergistically reduced axial force. Significant positive interactions were found between speed and depth, and between diameter and depth ( p < 0.05), suggesting deep drilling attenuated the force-reducing effects of high speed or large diameter. Region-related interactions were significant ( p < 0.05); the posterior region showed greater sensitivity to both high speed (more force reduction) and large diameter (more force increase). The results indicate that both drilling parameters and bone density have a significant impact on the axial force generated during the robotic implantation procedure. As bone density increases, the axial force tends to rise; whereas with increases in drill bit diameter, rotational speed, and drilling depth, the axial force generally exhibits a decreasing trend. Further analysis reveals that adjusting a single parameter is insufficient for achieving precise control over the drilling process, and the synergistic effects among multiple parameters must be considered comprehensively. Regarding the interaction effects, the combination of a high rotational speed and a large drill bit diameter can synergistically reduce the axial force; however, under conditions of greater drilling depth, the force-reducing effect induced by either high rotational speed or large diameter is substantially weakened.